As internal combustion engines are required to achieve greater efficiency, it becomes increasingly important to understand the combustion process and the state of the in-cylinder charge prior to combustion. A better understanding of the in-cylinder charge motion and its composition can be used to improve engine and combustion chamber design.
A variety of new technologies to improve engine efficiency call for new diagnostics and analysis methods, particularly of the combustion charge. For example, variable Miller cycle engines are effective at reducing pumping work and increasing expansion ratios. However, the in-cylinder change motion generated during induction decomposes into turbulence in a manner that is highly sensitive to timing of the intake valve's opening and closing.
As another example, by determining values for total inert dilution when operating engines with internal exhaust gas recirculation, through phasing of the intake and exhaust valves or when using cooled external recirculated exhaust gas or a combination of internal and external recirculated exhaust gas, useful prediction of combustion behavior can be made. However, determining total inert dilution levels in real time on a running engine can be challenging with current diagnostic and analysis methods.
As a third example, dedicated exhaust gas recirculation with in-cylinder reformation introduces high levels of untraditional compounds, specifically H2 and CO. The ability to predict the charge characteristics in real time would be beneficial for engine control and calibration purposes.